This invention pertains to refractory gun mixes, particularly such mixes containing a significant portion of stabilized lime aggregate.
Both the refractories producer and the refractories user have sought for many years to reduce their costs, for example by searching for lower cost refractory aggregates.
One very abundant, and therefore low cost, material of great refractoriness is lime (CaO). However, this material shows such a marked tendency to hydrate in the presence of any moisture, and also to form calcium carbonate (CaCO.sub.3) in the presence of carbon dioxide (CO.sub.2), that it is essentially useless as a refractory material, except in the most specialized circumstances.
Another very abundant, low cost source of refractory aggregate is dolomite, a roughly equimolar mixture of magnesium and calcium carbonates. This material is widely used as a refractory raw material, particularly in Europe, but also to a significant extent in the United States. However, it too suffers from the tendency of the lime contained in it to hydrate, and special precautions must be taken in using dolomite refractories to deal with this hydration tendency.
The present invention is directed to the use of another relatively low cost refractory material, the material referred to herein as "stabilized lime aggregate." While this material can be obtained from various sources, because of their great abundance and relative low cost, slags, for example slags from steelmaking processes, have proved to be a good source of this stabilized lime aggregate.
The use of slags in refractory materials has long been known; for example, U.S. Ser. No. 710,916 suggests the use of slag in a ramming mix for lining converters or furnaces. The use of slag is also suggested in U.S. Pat. No. 3,798,043, U.S. Pat. No. 4,222,786 and in British Application No. 2,058,041. However, the slags suggested for use in these patents differ significantly from the materials used in the practice of the present invention.